Chapter 23

Many transition metal complexes are brightly colored. Why is the titanium(IV) compound budotitane be colorless?

Is the glucose tolerance factor that contains chromium(III) paramagnetic or diamagnetic?

Coordination complexes containing paramagnetic transition metal ions make the best MRI contrast agents. a. Which of the first-row transition metal cations with a 2+ cations have the most unpaired valence electrons in the gas phase? b. Which of the first-row transition metal cations with a 2+ cations have the most unpaired valence electrons in octahedral coordination complexes?

The complexation of mercury(II) ion with methionine $$\mathrm{Hg}^{2+}+\text { methionine } \rightleftharpoons \mathrm{Hg}(\text { methionine })^{2+}$$ has a formation constant of \(\log K_{\mathrm{f}}=14.2,\) whereas the formation constant for the \(\mathrm{Hg}^{2+}\) complex with penicillamine $$\mathrm{Hg}^{2+}+\text { penicillamine } \rightleftharpoons \mathrm{Hg} \text { (penicillamine) }^{2+}$$ is \(\log K_{\mathrm{f}}=16.3 .\) Calculate the equilibrium constant for the reaction Hg(methionine) \(^{2+}+\) penicillamine \(\rightleftharpoons\) Hg(penicillamine) \(^{2+}+\) methionine

The complexation of mercury(II) ion with cysteine in aqueous solution $$\mathrm{Hg}^{2+}+\text { cysteine } \rightleftharpoons \mathrm{Hg}(\text { cysteine })^{2+}$$ has a formation constant of \(\log K_{f}=14.2,\) whereas the formation constant for the \(\mathrm{Hg}^{2+}\) complex with glycine $$\mathrm{Hg}^{2+}+\text { glycine } \rightleftharpoons \mathrm{Hg}(\text { glycine })^{2+}$$ is \(\log K_{\mathrm{f}}=10.3 .\) Calculate the equilibrium constant for the reaction Hg(cysteine) \(^{2+}+\) glycine \(\rightleftharpoons\) Hg(glycine) \(^{2+}+\) cysteine

Dissolving cobalt(II) nitrate in water gives a beautiful purple solution. There are three unpaired electrons in this cobalt(II) complex. When cobalt(II) nitrate is dissolved in aqueous ammonia and oxidized with air, the resulting yellow complex has no unpaired electrons. Which cobalt complex has the larger crystal field splitting energy \(\Delta_{o} ?\)

A solid compound containing \(\mathrm{Fe}(\mathrm{II})\) in an octahedral crystal field has four unpaired electrons at \(298 \mathrm{K} .\) When the compound is cooled to \(80 \mathrm{K},\) the same sample appears to have no unpaired electrons. How do you explain this change in the compound's properties?

When \(\mathrm{Ag}_{2} \mathrm{O}\) reacts with peroxodisulfate \(\left(\mathrm{S}_{2} \mathrm{O}_{8}^{2-}\right)\) ion (a powerful oxidizing agent), \(\mathrm{AgO}\) is produced. Crystallographic and magnetic analyses of AgO suggest that it is not simply \(\mathrm{Ag}(\mathrm{II})\) oxide, but rather a blend of \(\mathrm{Ag}(\mathrm{I})\) and \(\mathrm{Ag}(\mathrm{III})\) in a square planar environment. The \(\mathrm{Ag}^{2+}\) ion is paramagnetic but, like \(\mathrm{AgO}, \mathrm{Ag}^{+}\) and \(\mathrm{Ag}^{3+}\) are diamagnetic. Explain why.

The iron(II) compound Fe(bipy) \(_{2}(\mathrm{SCN})_{2}\) is paramagnetic, but the corresponding cyanide compound \(\mathrm{Fe}(\text { bipy })_{2}(\mathrm{CN})_{2}\) is diamagnetic. Why do these two compounds have different magnetic properties?

Aqueous solutions of copper(II)-ammonia complexes are dark blue. Will the color of the series of complexes \(\mathrm{Cu}\left(\mathrm{H}_{2} \mathrm{O}\right)_{(6-x)}\left(\mathrm{NH}_{3}\right)_{x}^{+}\) shift toward shorter or longer wavelengths as the value of \(x\) increases from 0 to \(6 ?\)

Manganese(II) chloride was one of the first compounds to be investigated as MRI contrast agents. How many unpaired electrons does the complex have when \(\mathrm{MnCl}_{2}\) dissolves in water to form the coordination compound \(\mathrm{MnCl}_{2}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4} ?\)

Gadolinium(III) ions are used in contrast agents for MRI because they have unpaired electrons. What is the electron configuration for Gd \(^{3+}\) and how many unpaired electrons does it have?